I am glad you figured it out. There's not only an H5P plugin for moodle, but also for other systems such as WordPress, drupal, etc. and the easy solution back when H5P was created was to simply name the required core version. Feel free to add a feature request stating that there should be something like a lookup-table for all the plugins and the core versions or some other mechanism that would allow to name the required plugin version instead of the core version. However, this might require some other changes as well.